Testing for Sleep Apnoea

What is Sleep Apnoea and How do we Test for it?

The standard way of testing for sleep apnoea is by using a full diagnostic polysomnographic (PSG) or sleep study. This is a very comprehensive test which was developed as a research tool in the 1960s to study sleep physiology and has become the ‘gold standard’ test to diagnose sleep disorders and guide treatment. It is expensive and time consuming to perform, analyse and report.

There are many sleep disorders, but obstructive sleep apnoea (OSA) where the airway collapses, and central sleep apnoea – Cheyne-Stokes respiration (CSA ) – where no attempt to breath is made, as well as combinations of the two (mixed apnoea), are common in patients with heart disease.

OSA is known to cause hypertension (and to make it resistant to drug treatment), left ventricular hypertrophy, coronary disease and stroke as well as cardiac arrhythmias including atrial fibrillation and sudden cardiac death.

Snoring is common; only about 1 in 3 heavy snorers has OSA but it is possible to have OSA and not snore. In OSA the airway collapses during sleep and repeated attempts to open it cause patients to wake up and make snoring and choking noises as they do so.

Central sleep apnoea is nearly always caused by heart failure and is either not associated with snoring or snoring may have reduced as a result developing CSA. In CSA, patients alternate between over breathing (hyperventilation) and not attempting to breathe (central apnoea). Central apnoeas are quiet.

Sleepiness is part of Obstructive Sleep Apnoea Syndrome (OSAS) but only 1 in 4 patients in the community with OSA (5 or more breathing stoppages/hour of sleep) is sleepy. The heart and vascular complications of OSA are generally not related to sleepiness but to the severity of breathing disturbance during sleep.

We use home testing as the initial test in most patients and may need to repeat it if the recording time is too short (under 4 hours) or the patient is aware that they did not sleep. If OSA or CSA is present we may opt to go straight onto a trial of treatment with an experienced therapist or refer the patient for an overnight diagnostic sleep (PSG) study in an attended setting such as RPAH or another Sleep Laboratory.

Simple At-Home Sleep Study – ApneaLink

The Apnoea Link is a device designed to monitor your breathing and blood oxygen levels during sleep. The test is relatively simple using up to 3 measurements including airflow, blood oxygen levels and breathing efforts. The test is much easier to do and much quicker to analyse than a conventional sleep study done in a laboratory. In some patients we are able to get all the information we need to start treatment for sleep apnoea and in others more detailed studies are needed especially if more complicated sleep disorders are present.

There are many home sleep monitors (Helpful Links: Sleep Apnoea) but we use the ResMed ApneaLink. The study consists of a monitor strapped around your waist, a set of small nasal prongs which measures air flow through the nose, a finger piece oximeter to measure your blood oxygen levels through the skin and in some, but not all, patients, a waistband which measures breathing effort. A technician will show you how to correctly fit the monitor at home.